Answer:
c. improper input handling on the FTP site
Explanation:
Improper input handling on the FTP site is associated with encrypting and/or decrypting of input data. It has been observed that input handling on the FTP site is one of the leading causes of vulnerabilities found in contemporary's systems and applications, this is a result of application trusting which helps to establish restrictions and prevent Improper Input Handling attacks accurately.
Hence, in this case, the correct answer is "improper input handling on the FTP site"